MIAMI - A Canadian diplomat sobbed on the witness stand Friday as she said her 15-year-old son, who could be jailed for life if convicted of murder, is a child every parent would want.

Testifying at his bail hearing, Roxanne Dube described Marc Wabafiyebazu as quiet, intelligent, polite and with no history of fighting or violence.

"I am absolutely convinced of Marc's innocence," Dube said as she pledged to be his surety if he's released. "He's a good boy. He never had any issues whatsoever."

Dube, currently on leave as Canada's consul general in Miami, quickly regained her composure as she said her son lacked self-confidence because of a learning disability. She said he was also "highly influenced" by his older brother Jean Wabafiyebazu, 18, who along with another teen was gunned down March 30.

Police allege the older sibling and Joshua Wright, 17, shot each other fatally during the botched robbery of dealer Anthony Rodriguez while Marc Wabafiyebazu waited outside.

Dube, who said she "just wept" when police told her that her son had been charged with felony murder, said she could put up $25,000 bail for her son, given her relatively limited resources.

Much of the state's felony murder case against the Ottawa teen — he has pleaded not guilty — relies on an allegedly spontaneous confession he gave a rookie patrol officer who was driving him to a detention centre.

It was only after the distraught teen blurted out the self-incriminating statements that what had been a misdemeanour arrest became a murder case.

However, officer Juan Velez admitted some of the most important details of what he said Wabafiyebazu told him have since been shown to be wrong.

Those details include the teen's apparent admission that he sat behind the wheel as getaway driver while his older brother went inside a Miami apartment to rob a drug dealer.

In fact, surveillance video shows the teen, who had turned 15 less than two weeks earlier and had never driven in his life, did not get into the driver's seat.

Velez said he was touched by the teen's plight and offered "positive words" of encouragement during the ride to the holding centre.

"I was trying to cheer him up."

Following the pep talk, Wabafiyebazu blurted out a "stream" of incriminating statements, Velez said.

"I know you're a police officer but everyone is going to talk, so I may as well talk," Velez recounted the boy as saying.

Wabafiyebazu told the officer they had gone to rob a dealer of drugs, and that they had done this before on "numerous occasions." His brother was smart and knew what he was doing, Velez said the teen told him.

"He says it was a job gone wrong. It wasn't supposed to go like that."

Velez explained that he did not try to interrogate his back-seat passenger or read him his rights because he was not the arresting officer.

Defence lawyer Mark Corey heaped scorn on Velez's testimony prompted by the officer's over-eagerness to be in on a big case.

"The testimony he gave is frankly absurd," said the lawyer.

Corey said there was no evidence his unarmed client participated in the robbery, was the getaway driver, or even guarded the vehicle — their mother's black BMW with diplomatic plates — as the prosecution has tried to argue.

Although he is more than six feet tall, Wabafiyebazu is hardly an intimidating presence, Corey said.

"He may look tall, but he is a baby," Corey said. "He is still frankly a boy."

Even if Wabafiyebazu knew what his older brother was planning, it would not be sufficient to charge him with felony murder, the lawyer said.

In her closing submissions, prosecutor Marie Mato used Wabafiyebazu's alleged statements to impugn his innocence.

"Those are not the words of someone who does not know what is going on," Mato said.

"He didn't even have to be there at all but the fact is that he was. He was there to assist his brother in the rip. He's in on it from beginning to end."

Justice Teresa Pooler reserved her decision until Wednesday.

Note to readers: This is a corrected story. Jean Wabafiyebazu was 18. Initial police reports had listed him as 17.